Possible Causes

Flexible Fuel (FF) sensor is a capacitive device with a signal processing stage. FF sensor determines percentage of ethanol in fuel. As percentage of ethanol in fuel mixture increases, output frequency of sensor will increase. PCM uses this information to calculate the correct air/fuel ratio and spark advance for vehicle operation. Possible causes are:

• Open or short in FF sensor VPWR circuit.
• Open in battery ground to FF sensor circuit.
• Open in FF sensor signal circuit.
• Short to ground in FF sensor signal circuit.
• Fuel contamination.
• Short to VPWR in FF sensor battery ground circuit.
• Short to VPWR in FF sensor signal circuit.
• Fuel separation.
• Damaged FF sensor.
• Damaged PCM.